DARPA commissions Sun optical interconnects

The Defense Advanced Research Projects Agency has commissioned Sun Microsystems to develop a microprocessor interconnect that will transmit data by light pulses rather than electrical currents, the company announced this month.

DARPA's Ultraperformance Nanophotonic Intrachip Communications (UNIC) program awarded the contract, which will run $44.29 million over five-and-a-half years.

"The program is about bringing optics much deeper into the interconnect hierarchy inside a computer. Right now, there's a lot of optical interconnects at the periphery of the system and to connect between boxes and between racks of servers. But really, the optical technologies have not penetrated inside the box," said Ashok Krishnamoorthy, an engineer at the Sun Microelectronics Group, in a podcast.

Silicon-based optical interconnects promise higher bandwidth and lower latency than today's electrical interconnects, which means data can be moved on and off microprocessors, or among multiple processors on the same circuit board, more quickly. Such interconnects would interest the high-performance computing community in particular, which must run massive programs across thousands of processors.

"DARPA's UNIC program will demonstrate high-performance photonic technology for high bandwidth, on-chip, photonic communications networks for advanced (≥ 10 trillion operations [per] second) microprocessors," said Jag Shah, DARPA Microsystems Technology Office program manager, in a statement. "By restoring the balance between computation and communications, the program will significantly enhance [the Defense Department's] capabilities for applications such as image processing, autonomous operations [and] synthetic-aperture radar as well as supercomputing."

Sun will apply research it completed previously for DARPA's High Productivity Computing Systems program. In that work, the company developed on-chip connectors, called Proximity Communication, which eliminate the need for sockets and pins.

Sun is not the only company interested in silicon-based optical interconnects. Last year, Intel announced that it had developed a laser modulator that could encode data at a rate of 40 billion bits per second.

"What we have today with electrical interconnects is [the ability] to achieve a signaling [rate] of a terabit per-second per-centimeter squared," of circuitry, Krishnamoorthy said. "What this program is about is trying to understand how to improve the density of communication by two or three orders of magnitude."

About the Author

Joab Jackson is the senior technology editor for Government Computer News.